In recent years, there is used a configuration in which a semiconductor device such as an MMIC (Monolithic Microwave Integrated Circuit) and a high-frequency package substrate is flip-chip assembled on another substrate by a BGA (Ball Grid Array) that uses solder bumps. In this configuration, there are cases where gold bumps are used instead of solder bumps.
Conventionally, even if a semiconductor device is mounted on a substrate using an electrically-conductive adhesive or the like, when the semiconductor device is covered by a metal cover to airtightly seal the semiconductor device or when ventilation holes are small even though the metal cover is not a type that airtightly seals the semiconductor device, a high-frequency signal is not leaked from the semiconductor device to outside. Therefore, there has been no problem regarding EMI (ElectroMagnetic Interference) characteristics (see Patent Literature 1).